1 // SPDX-License-Identifier: GPL-2.0
3 * class.c - basic device class management
5 * Copyright (c) 2002-3 Patrick Mochel
6 * Copyright (c) 2002-3 Open Source Development Labs
7 * Copyright (c) 2003-2004 Greg Kroah-Hartman
8 * Copyright (c) 2003-2004 IBM Corp.
11 #include <linux/device/class.h>
12 #include <linux/device.h>
13 #include <linux/module.h>
14 #include <linux/init.h>
15 #include <linux/string.h>
16 #include <linux/kdev_t.h>
17 #include <linux/err.h>
18 #include <linux/slab.h>
19 #include <linux/blkdev.h>
20 #include <linux/mutex.h>
23 #define to_class_attr(_attr) container_of(_attr, struct class_attribute, attr)
25 static ssize_t class_attr_show(struct kobject *kobj, struct attribute *attr,
28 struct class_attribute *class_attr = to_class_attr(attr);
29 struct subsys_private *cp = to_subsys_private(kobj);
33 ret = class_attr->show(cp->class, class_attr, buf);
37 static ssize_t class_attr_store(struct kobject *kobj, struct attribute *attr,
38 const char *buf, size_t count)
40 struct class_attribute *class_attr = to_class_attr(attr);
41 struct subsys_private *cp = to_subsys_private(kobj);
44 if (class_attr->store)
45 ret = class_attr->store(cp->class, class_attr, buf, count);
49 static void class_release(struct kobject *kobj)
51 struct subsys_private *cp = to_subsys_private(kobj);
52 struct class *class = cp->class;
54 pr_debug("class '%s': release.\n", class->name);
56 if (class->class_release)
57 class->class_release(class);
59 pr_debug("class '%s' does not have a release() function, "
60 "be careful\n", class->name);
65 static const struct kobj_ns_type_operations *class_child_ns_type(struct kobject *kobj)
67 struct subsys_private *cp = to_subsys_private(kobj);
68 struct class *class = cp->class;
70 return class->ns_type;
73 static const struct sysfs_ops class_sysfs_ops = {
74 .show = class_attr_show,
75 .store = class_attr_store,
78 static struct kobj_type class_ktype = {
79 .sysfs_ops = &class_sysfs_ops,
80 .release = class_release,
81 .child_ns_type = class_child_ns_type,
84 /* Hotplug events for classes go to the class subsys */
85 static struct kset *class_kset;
88 int class_create_file_ns(struct class *cls, const struct class_attribute *attr,
94 error = sysfs_create_file_ns(&cls->p->subsys.kobj,
101 void class_remove_file_ns(struct class *cls, const struct class_attribute *attr,
105 sysfs_remove_file_ns(&cls->p->subsys.kobj, &attr->attr, ns);
108 static struct class *class_get(struct class *cls)
111 kset_get(&cls->p->subsys);
115 static void class_put(struct class *cls)
118 kset_put(&cls->p->subsys);
121 static struct device *klist_class_to_dev(struct klist_node *n)
123 struct device_private *p = to_device_private_class(n);
127 static void klist_class_dev_get(struct klist_node *n)
129 struct device *dev = klist_class_to_dev(n);
134 static void klist_class_dev_put(struct klist_node *n)
136 struct device *dev = klist_class_to_dev(n);
141 static int class_add_groups(struct class *cls,
142 const struct attribute_group **groups)
144 return sysfs_create_groups(&cls->p->subsys.kobj, groups);
147 static void class_remove_groups(struct class *cls,
148 const struct attribute_group **groups)
150 return sysfs_remove_groups(&cls->p->subsys.kobj, groups);
153 int __class_register(struct class *cls, struct lock_class_key *key)
155 struct subsys_private *cp;
158 pr_debug("device class '%s': registering\n", cls->name);
160 cp = kzalloc(sizeof(*cp), GFP_KERNEL);
163 klist_init(&cp->klist_devices, klist_class_dev_get, klist_class_dev_put);
164 INIT_LIST_HEAD(&cp->interfaces);
165 kset_init(&cp->glue_dirs);
166 __mutex_init(&cp->mutex, "subsys mutex", key);
167 error = kobject_set_name(&cp->subsys.kobj, "%s", cls->name);
173 /* set the default /sys/dev directory for devices of this class */
175 cls->dev_kobj = sysfs_dev_char_kobj;
177 #if defined(CONFIG_BLOCK)
178 /* let the block class directory show up in the root of sysfs */
179 if (!sysfs_deprecated || cls != &block_class)
180 cp->subsys.kobj.kset = class_kset;
182 cp->subsys.kobj.kset = class_kset;
184 cp->subsys.kobj.ktype = &class_ktype;
188 error = kset_register(&cp->subsys);
193 error = class_add_groups(class_get(cls), cls->class_groups);
196 kobject_del(&cp->subsys.kobj);
197 kfree_const(cp->subsys.kobj.name);
202 EXPORT_SYMBOL_GPL(__class_register);
204 void class_unregister(struct class *cls)
206 pr_debug("device class '%s': unregistering\n", cls->name);
207 class_remove_groups(cls, cls->class_groups);
208 kset_unregister(&cls->p->subsys);
211 static void class_create_release(struct class *cls)
213 pr_debug("%s called for %s\n", __func__, cls->name);
218 * __class_create - create a struct class structure
219 * @owner: pointer to the module that is to "own" this struct class
220 * @name: pointer to a string for the name of this class.
221 * @key: the lock_class_key for this class; used by mutex lock debugging
223 * This is used to create a struct class pointer that can then be used
224 * in calls to device_create().
226 * Returns &struct class pointer on success, or ERR_PTR() on error.
228 * Note, the pointer created here is to be destroyed when finished by
229 * making a call to class_destroy().
231 struct class *__class_create(struct module *owner, const char *name,
232 struct lock_class_key *key)
237 cls = kzalloc(sizeof(*cls), GFP_KERNEL);
245 cls->class_release = class_create_release;
247 retval = __class_register(cls, key);
255 return ERR_PTR(retval);
257 EXPORT_SYMBOL_GPL(__class_create);
260 * class_destroy - destroys a struct class structure
261 * @cls: pointer to the struct class that is to be destroyed
263 * Note, the pointer to be destroyed must have been created with a call
266 void class_destroy(struct class *cls)
268 if (IS_ERR_OR_NULL(cls))
271 class_unregister(cls);
275 * class_dev_iter_init - initialize class device iterator
276 * @iter: class iterator to initialize
277 * @class: the class we wanna iterate over
278 * @start: the device to start iterating from, if any
279 * @type: device_type of the devices to iterate over, NULL for all
281 * Initialize class iterator @iter such that it iterates over devices
282 * of @class. If @start is set, the list iteration will start there,
283 * otherwise if it is NULL, the iteration starts at the beginning of
286 void class_dev_iter_init(struct class_dev_iter *iter, struct class *class,
287 struct device *start, const struct device_type *type)
289 struct klist_node *start_knode = NULL;
292 start_knode = &start->p->knode_class;
293 klist_iter_init_node(&class->p->klist_devices, &iter->ki, start_knode);
296 EXPORT_SYMBOL_GPL(class_dev_iter_init);
299 * class_dev_iter_next - iterate to the next device
300 * @iter: class iterator to proceed
302 * Proceed @iter to the next device and return it. Returns NULL if
303 * iteration is complete.
305 * The returned device is referenced and won't be released till
306 * iterator is proceed to the next device or exited. The caller is
307 * free to do whatever it wants to do with the device including
308 * calling back into class code.
310 struct device *class_dev_iter_next(struct class_dev_iter *iter)
312 struct klist_node *knode;
316 knode = klist_next(&iter->ki);
319 dev = klist_class_to_dev(knode);
320 if (!iter->type || iter->type == dev->type)
324 EXPORT_SYMBOL_GPL(class_dev_iter_next);
327 * class_dev_iter_exit - finish iteration
328 * @iter: class iterator to finish
330 * Finish an iteration. Always call this function after iteration is
331 * complete whether the iteration ran till the end or not.
333 void class_dev_iter_exit(struct class_dev_iter *iter)
335 klist_iter_exit(&iter->ki);
337 EXPORT_SYMBOL_GPL(class_dev_iter_exit);
340 * class_for_each_device - device iterator
341 * @class: the class we're iterating
342 * @start: the device to start with in the list, if any.
343 * @data: data for the callback
344 * @fn: function to be called for each device
346 * Iterate over @class's list of devices, and call @fn for each,
347 * passing it @data. If @start is set, the list iteration will start
348 * there, otherwise if it is NULL, the iteration starts at the
349 * beginning of the list.
351 * We check the return of @fn each time. If it returns anything
352 * other than 0, we break out and return that value.
354 * @fn is allowed to do anything including calling back into class
355 * code. There's no locking restriction.
357 int class_for_each_device(struct class *class, struct device *start,
358 void *data, int (*fn)(struct device *, void *))
360 struct class_dev_iter iter;
367 WARN(1, "%s called for class '%s' before it was initialized",
368 __func__, class->name);
372 class_dev_iter_init(&iter, class, start, NULL);
373 while ((dev = class_dev_iter_next(&iter))) {
374 error = fn(dev, data);
378 class_dev_iter_exit(&iter);
382 EXPORT_SYMBOL_GPL(class_for_each_device);
385 * class_find_device - device iterator for locating a particular device
386 * @class: the class we're iterating
387 * @start: Device to begin with
388 * @data: data for the match function
389 * @match: function to check device
391 * This is similar to the class_for_each_dev() function above, but it
392 * returns a reference to a device that is 'found' for later use, as
393 * determined by the @match callback.
395 * The callback should return 0 if the device doesn't match and non-zero
396 * if it does. If the callback returns non-zero, this function will
397 * return to the caller and not iterate over any more devices.
399 * Note, you will need to drop the reference with put_device() after use.
401 * @match is allowed to do anything including calling back into class
402 * code. There's no locking restriction.
404 struct device *class_find_device(struct class *class, struct device *start,
406 int (*match)(struct device *, const void *))
408 struct class_dev_iter iter;
414 WARN(1, "%s called for class '%s' before it was initialized",
415 __func__, class->name);
419 class_dev_iter_init(&iter, class, start, NULL);
420 while ((dev = class_dev_iter_next(&iter))) {
421 if (match(dev, data)) {
426 class_dev_iter_exit(&iter);
430 EXPORT_SYMBOL_GPL(class_find_device);
432 int class_interface_register(struct class_interface *class_intf)
434 struct class *parent;
435 struct class_dev_iter iter;
438 if (!class_intf || !class_intf->class)
441 parent = class_get(class_intf->class);
445 mutex_lock(&parent->p->mutex);
446 list_add_tail(&class_intf->node, &parent->p->interfaces);
447 if (class_intf->add_dev) {
448 class_dev_iter_init(&iter, parent, NULL, NULL);
449 while ((dev = class_dev_iter_next(&iter)))
450 class_intf->add_dev(dev, class_intf);
451 class_dev_iter_exit(&iter);
453 mutex_unlock(&parent->p->mutex);
458 void class_interface_unregister(struct class_interface *class_intf)
460 struct class *parent = class_intf->class;
461 struct class_dev_iter iter;
467 mutex_lock(&parent->p->mutex);
468 list_del_init(&class_intf->node);
469 if (class_intf->remove_dev) {
470 class_dev_iter_init(&iter, parent, NULL, NULL);
471 while ((dev = class_dev_iter_next(&iter)))
472 class_intf->remove_dev(dev, class_intf);
473 class_dev_iter_exit(&iter);
475 mutex_unlock(&parent->p->mutex);
480 ssize_t show_class_attr_string(struct class *class,
481 struct class_attribute *attr, char *buf)
483 struct class_attribute_string *cs;
485 cs = container_of(attr, struct class_attribute_string, attr);
486 return sysfs_emit(buf, "%s\n", cs->str);
489 EXPORT_SYMBOL_GPL(show_class_attr_string);
491 struct class_compat {
492 struct kobject *kobj;
496 * class_compat_register - register a compatibility class
497 * @name: the name of the class
499 * Compatibility class are meant as a temporary user-space compatibility
500 * workaround when converting a family of class devices to a bus devices.
502 struct class_compat *class_compat_register(const char *name)
504 struct class_compat *cls;
506 cls = kmalloc(sizeof(struct class_compat), GFP_KERNEL);
509 cls->kobj = kobject_create_and_add(name, &class_kset->kobj);
516 EXPORT_SYMBOL_GPL(class_compat_register);
519 * class_compat_unregister - unregister a compatibility class
520 * @cls: the class to unregister
522 void class_compat_unregister(struct class_compat *cls)
524 kobject_put(cls->kobj);
527 EXPORT_SYMBOL_GPL(class_compat_unregister);
530 * class_compat_create_link - create a compatibility class device link to
532 * @cls: the compatibility class
533 * @dev: the target bus device
534 * @device_link: an optional device to which a "device" link should be created
536 int class_compat_create_link(struct class_compat *cls, struct device *dev,
537 struct device *device_link)
541 error = sysfs_create_link(cls->kobj, &dev->kobj, dev_name(dev));
546 * Optionally add a "device" link (typically to the parent), as a
547 * class device would have one and we want to provide as much
548 * backwards compatibility as possible.
551 error = sysfs_create_link(&dev->kobj, &device_link->kobj,
554 sysfs_remove_link(cls->kobj, dev_name(dev));
559 EXPORT_SYMBOL_GPL(class_compat_create_link);
562 * class_compat_remove_link - remove a compatibility class device link to
564 * @cls: the compatibility class
565 * @dev: the target bus device
566 * @device_link: an optional device to which a "device" link was previously
569 void class_compat_remove_link(struct class_compat *cls, struct device *dev,
570 struct device *device_link)
573 sysfs_remove_link(&dev->kobj, "device");
574 sysfs_remove_link(cls->kobj, dev_name(dev));
576 EXPORT_SYMBOL_GPL(class_compat_remove_link);
578 int __init classes_init(void)
580 class_kset = kset_create_and_add("class", NULL, NULL);
586 EXPORT_SYMBOL_GPL(class_create_file_ns);
587 EXPORT_SYMBOL_GPL(class_remove_file_ns);
588 EXPORT_SYMBOL_GPL(class_unregister);
589 EXPORT_SYMBOL_GPL(class_destroy);
591 EXPORT_SYMBOL_GPL(class_interface_register);
592 EXPORT_SYMBOL_GPL(class_interface_unregister);